This program of projects is a continuing investigation of the effects of injury to spinal nerves or to spinal cord tracts upon the functional organization of vertebrate spinal neurons. The overall goal of this program is to provide data on the degree that functionally-effective regeneration or reorganization of spinal neurons and their connections can take place in immature or mature vertebrate nervous systems. Each of the projects has its counterpart or point of departure in deficits suffered by human beings after disease or traumatic injury of the spinal cord and/or of the nervous processes of spinal neurons. The approaches are interdisciplinary and employ animal models in which combinations of physiological, morphological, biochemical and behavioral measures are combined in various ways to test for examples of: a) regeneration or reorganization of spinal pathways in vertebrates, b) changes in the organization of spinal reflexes involving the kidney and bladder after spinal cord injury, c) conditions favoring functionally effective reinnervation of the urinary bladder by foreign nerves, d) factors associated with the specificity of reinnervation and regeneration after injury of sympathetic preganglionic neurons, e) changes in utilization of amino acids and associated modification in cytoskeletal protein synthesis by motoneuron cell bodies after injury of their axons, f) modifications of the projections into the spinal cord of thin afferent fibers after injury of dorsal roots and associated alterations in functional properties of neurons in laminae I and II, and g) modifications in the distribution of chemical markers for primary afferent fibers such as peptides in the spinal gray matter after injury of ascending spinal pathways.